n - PATh :.: Process and Product Applied Thermodynamics research ...

P / MPa
14
12
10
8
6
4
2
0
0.0 0.2 0.4 0.6 0.8 1.0
x, y CO2
Modeling
Figure III.13. Predictions of VLE of CO2/perfluobenzene system at 293.15, 323.15 and 353.15 K.
Symbols represent experimental data measured in this work. Solid dark lines correspond to the
soft-SAFT model including the polar term and dashed lines to the original soft-SAFT model. In
both cases the size and the energy binary interaction parameters are set to one. The lighter solid
lines are predictions given by the Peng Robinson EoS with kij=0.
Results obtained for perfluorodecalin and perfluoromethylcyclohexane are similar
to the ones obtained for perfluoro-n-octane, meaning that the introduction of the
quadrupole effect in CO2 does not seem to noticeably influence the description of the phase
equilibria for non aromatic perfluorocompounds.
In a previous work, it was observed that binary parameters are needed for obtaining
quantitative predictions if the lengths of the two molecules involved in the mixtures are
different and/or their shape deviates from spherical (Kontogeorgis et al., 1996). Using
other EoS the authors showed that for athermal mixtures the use of a size binary parameter
could provide a better and more meaningful description of data and reduce the magnitude
of the energy binary parameter in systems were energetic interactions are important. Thus,
a good description of the phase diagrams of CO2/non-aromatic-perfluoroalkanes requires
the use of two interaction parameters, as previously observed for oxygen/perfluoroalkanes
mixtures.
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